Process and apparatus for producing spherical metal pellets



April ll, 1961 L. w. BLIEMEISTER PROCESS AND APPARATUS PRODUCINGSPHERICAL METAL PELLETS Filed Feb. 8, 1960 3 Sheets-Sheet 1 April 11,1961 l.. w. Bur-:MEISTER 2,978,742

PRocEss AND APPARATUS PRoDucING sPHERIcAL METAL PELLETs Filed Feb. 8,1960 3 Sheets-Sheet 2 April 11, 1961 L.. w. BLIEMEISTER 2,978,742

PRocEss AND APPARATUS PRoDUcING sPHERIcAL METAL PELLETs Filed Feb. 8,1960 3 Sheets-Sheet 3 lnited States Patent PROCESS AND APPARATUS FOR`PRODUCING 'SPHERICAL METAL PELLE'IS Louis W. Bliemeister, 5410 W. 99thSt., Los Angeles 45, Calif.

Filed Feb. 8, 1960, Ser. No. 7,241

11 Claims. (Cl. 1.8-2.4)

This vinvention relates to a process and apparatus for the production ofsphericalmetal pellets and, more particularly, relates to the productionof shot from low melting lead alloys.

One of the problems to which the invention is directed is to provide alow cost, compact, high production apparatus of this type. Such anapparatus may be installed and operated economically at numerouswidespread locations to achieve decentralization of this industry.Decentralization is desirable for a number of reasons, and especiallyfor reduction in shipping costs. The apparatus of the present inventionfor the production ofshot of various sizes, together with associatedequipment for processing, classifying and packing the shot, may beinstalled in an ordinary industrial room at moderate cost and may beoperated with full eciency by a single operator.

A second problem is to achieve a high percentage of any selected size ofshot in a production run. The solution to -this problem requires theproduction of uniform drops of melted metal and an efficient procedurefor converting the molten drops into spherical pellets. The presentinvention produces more than 80% of selected sizes of shot and, in someinstances, more than 90%. In this regard, a special feature of Itheinvention is the ease and speed with which a transition may be made fromthe production of one size of shot to the production of another size.

A third problem that is important in some instances is to minimizeoxidation of the product. Some degree of oxidation is inevitable when ahighly heated metal is exposed to the atmosphere. The inventionsubstantially eliminates such exposure.

The invention is based largely on the discovery that bodies of meltedmetal in the form of drops can be converted to solid spherical bodies inthe course of falling through a body of quenching liquid of moderatedepth, for example, of a depth substantially less than six feet,provided that the fall of the melted bodies through the quenching liquidis interrupted and moderate spin is imparted to the bodies while theyare still molten. It has been discovered that the fall of the metaldrops may be interrupted or blocked in a desirable manner by placing amember in the vquenching liquid across the path of fall, which memberpresents an absorbent surface of low thermal conductivity, such as asurface of wood. The exceedingly hot metal of a falling body vaporizesthe contiguous quenching liquid and the falling body may be observed torebound from the blocking surface, apparently because of an interveningvapor cushion. The phenomenon is not fully understood but there isreason to believe that the presence of water absorbed in the surfacestructure of the blocking member is important and that the low thermalconductivity of the blocking member is also important.

The required moderate spin may be imparted to the melted metal bodies intwo different ways. In one arrangement, the blocking surface is simplyinclined to cause the decelerated molten bodies to gravitate to its edgewith rolling effect on the bodies. In another arrangement, a blockingdisc is rotated to cause the molten metal bodies to move to its edge bycentrifugal force. In each instance, spin is imparted to the moltenbodies by rolling contact and then the spinning bodies are released tocontinue to fall through the quenching liquid and to solidify whilefalling.

The drops of melted metal as they are initially formed in the air abovethe quenching liquid are, of course, elongated. They do not have animmediate opportunity to become spherical and especially so because ofthe disturbing transition from air to water. Apparently the interruptionin the fall of the melted bodies below the surface of the quenchingliquid is-important in permitting equalization of the forces that actonthe metal bodies in all directions and, apparently, the moderate spin ofthe bodies in vertical planes while the still molten eliminates theinitial vertical elongation of the bodies.

A feature of the preferred practice of the invention is a method ofproducing uniform liquid metal drops in quantity. The invention utilizesspecial feed passages at the bottom of a melted metal reservoir and, inaddition, vibrates the reservoir arid the feed passages to dislodge theformed drops. The vibration keeps the adjustment of the feed passagesfrom being critical. In the preferred practice of the invention, each ofthe dropforming feed passages includes registered apertures in twotransverse sheets that are clamped together face to face, both of theapertures being downwardly tapered and the upper or innermost aperturebeing the smaller aperture.

A further feature of one practice of the invention is the concept ofproviding a feed unit to supply the melted metal drops in combinationwith a plurality of tanks for use interchangeably and successively withthe feed unit. Each of the interchangeable tanks contains a body ofquenching liquid and is equipped with means for interrupting the fall ofthe molten bodies to impart spin to the molten bodies. When a desiredquantity of finished shot accumulates in one tank, the tank is replacedwith a second tank. The quenching liquid is drained from the replacedtank and the tank is used as a hopper to feed the shot therein tosuitable equipment for further processing.

The features and advantages of the invention lmay be understood from thefollowing detailed description and the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative: Y

Fig. 1 is a perspective view of a selected embodiment of the invention;

Fig. 2 is a fragmentary elevation viewed as indicated by the arrow 2 inFig. 1 and showing an adjustable overflow control to vary the level ofthe quenching liquid;

Fig. 3 is a fragmentary side elevation showing how a tank of quenchingliquid may be adjusted by screw means; l

Fig. 4 is an enlarged transverse cross section showing the constructionofthe feed unit for releasing the melted metal in drop form and alsoshowing the means in the quenching liquid for interrupting the fall ofthe metal bodies;

Fig. 5 is an enlarged portion of Fig. 4, which portion is indicated bythe arrow 5 in Fig. 4 and shows the construction of a drop-forming feedpassage;

Fig. 6 is a fragmentary sectional view showing a modied form of themeans for interrupting the fall of the metal bodies;

Fig. 7 is a similar view of a second modification of the interruptingmeans;

Fig. 8 is a fragmentary plan view of the feed unit and adjacentstructure;

Fig. 9 is a simplied diagrammatic view showing how a plurality of tanksfor quenching liquid may be used interchangeably with a feed unit;

Fig. l is a simplified diagrammatic plan view of a circular feed unitand a rotary means under the circular feed unit to interrupt the fall ofthe molten metal bodies and to impart spin to the molten bodies; and

Fig. 11 is a simplified side elevational view of the structure shown inFig. 10.

General arrangement The principal parts of the selected embodiment ofthe invention shown in Figs. l to 3 and 4 to 8 include: an uprightreceptacle or metal tank, generally designated 20, to contain a body ofquenching liquid 22 (Fig. 4); an overhead water pipe 24 with a valve 25for supplying water as needed to serve as the quenching liquid; anadjustable overflow outlet, generally designated V26 (Figs. 2 and 8) tocontrol the level of the quenching liquid in the tank; an uprightrectangular frame, generally designated 23straddling the tank 2u andseparate from the tank; a feed unit, generally designated 30, mounted onthe top of the frame 28 above the tank 20 to release drops of moltenmetal into the quenching liquid; a vibrator 32 mounted on the frame2S'to vibrate the feed unit 3i? to facilitate the dislodgement of thedrops of melted metal; a Crucible or pot 34 supported by a frame 35 formelting the metal; a pipe 36 extending from the pot 34 to the feed unit30 to supply the melted metal thereto; a valve 33 in the pipe 36 tocontrol the rate of supply of the melted metal; a member 40 (Fig. 4) inthe body of quenching liquid in the tank to interrupt the fall of themolten metal bodies and to impart spin to the molten metal bodies, thisinterrupting member being in the form of an inclined plate of suitablematerial, preferably pine or cypress; means in the form of a gas burner42 to heat the upper levels of the quenching liquid in the tank 20; anda heat exchange coil 43 to cool the lower levels of the liquid tofacilitate the solidifyingof the falling metal bodies.

The bottom of the tank 20 is enlarged to serve as a hopper for thefinished shot and preferably an inclined baie 44 is positioned to divertthe falling solidified shot for the purpose of distributing the shotover the enlarged bottom of the hopper. A glass vwindow 4S makes itpossible to observe the interior of the tank to ascertain when a desiredquantity of shot has been accumulated. A cylindrical port 46 forremoving shot from the bottom of the tank is provided with a removablecap 48 and the cap in turn is equipped with a faucet 50 to permit thetank to be drained before the cap is removed.

Operation The feed unit 30 has a row of feed apertures to producesuccessive drops of melted metal close to the surface of the quenchingliquid. The formed drops fall into the quenching liquid and areimmediately blocked by the interrupting member 4i?. The drops initiallytravel through the air a relatively short distance to reach the liquid,usually much less than an inch for minimum oxidation by the atmosphere.The metal bodies may be observed to rebound slightly from theinterrupting member 40 and to gravitate to the lower edge of theinterrupting member with the consequent impartation of spin to the metalbodies while they are still molten. The spinning metal bodies harden inthe course of their continued fall through the quenching liquid and arecornpletely solidified by the time they reach the deecting battle 44.

As will be explained later, the feed unit 3) is of a specialconstruction that forms uniform drops of liquid metal of a selectedsize, the feed unit being readily adjustable to change from one size toanother. Various adas a. lock nut.

justments lmay be made within the skill expected in this art to set theapparatus for the production of shot from different alloys in differentsizes. The distance through which the metal drops fall before they reachthe quenching liquid 22 may be varied by manipulating the adjustableoverflow outlet 26 to raise or lower the level of the quenching liquid.lIn general, it is desirable to reduce this distance for the largersizes of shot and it is also desirable to reduce the distance of theinterrupting member 40 below the surface of the quenching liquid.

The angle of inclination of the interrupting member 40 may best bebetween 10 and 20. An angle from horizontal of 17 gives good results forshot of sizes 8 and 9 (.090 inch diameter and .080 inch diameter)respectively. The angle should be decreased for increased sizes of shot.Por example, an angle of 12 is recommended for number 6 shot (.110 inchdiameter).

The length of the travel of the molten metal bodies along the inclinedsurface of the interrupting member 40 should be increased with increasein the sizes of shot and vice versa. For this purpose, the interruptingmember may be horizontally adjustable in the tank, but in the presentembodiment of the invention, it is contemplated that the tank will bemove-d horizontally relative to the feed unit whenever such anadjustment is desirable.

In the present practice of the invention, the quenching liquid is Water.Other liquids may be used, however, and in general higher liquiddensities are desirable for the larger shot sizes. The temperature ofthe water should be reduced slightly for the larger sizes. In general,the temperature to which the metal is heated is approximately above itsmelting point and the temperature of the quenching liquid isapproximately in the range of F.205 F. For number 9 shot, 205 F. isdesirable, and F. is desirable for the larger number 6 shot.

Structural details Gaseous fuel for the various burners may be obtainedfrom a supply pipe I52 which has a branch to the previously mentionedburner 42. Other branches supply fuel to a burner I54 under the meltingpot 34, a burner 55 (Figs. 1 and 4) that extends lengthwise of the feedunit 30, and a burner 56 under the bottom wall of the tank. The burner56 may be omitted but is useful to keep the water up to temperaturewhenever a production run is interrupted.

The tank 2i) is shaped to overhang the burner 42 that maintains theupper levels of the quenching liquid at a desired temperature. Theheating of the quenching liquid by the burner 42 releases gases from theliquid and causes a certain amount of vaporization of the liquid. Theconsequent bubbles should be free to rise to the top surface of thequenching liquid in a region well away from the paths of fall of themetal bodies from the interrupting member 40. As may be seen in Fig. 4,the upper end of the interrupting member' 4t? is spaced substantiallyfrom the adjacent wall 58 of the tank 20 to permit free travel of thebubbles past the upper end of the interrupting member. The upwardlytilted edge of the interrupting member serves as an effective barrier tokeep the bubbling action from disturbing the quenching liquid along theupper surface of the interrupting member.

As best shown in Fig. 4, the interrupting member 40 comprises a plate ofwood, for example pine or maple, which is hingedly mounted at its upperend on a cross rod 60 by means of a fitting 62. The cross rod 60 issupported at each end by a screw 64 in a support bracket 35, the screwbeing adjustable to raise or lower the cross rod. The lower edge of theinterrupting member 4t? may be adjustably supported by a pair of uprightscrew members 66 which are pivotally connected to the interruptingmember. Each of the screws extends through a fixed unthreadcd supportbushing 68 and through a knurled adjustment nut 70. A winged nut 72 maybe added to serve The previously mentioned adjustable overflow outlet 26comprises an opening in the upper edge of the tank 20 and a gate orangular blade '74 which serves as an adjustable edge of the opening.'Ihe gate 74 is pivotally mounted on a screw 75 which is equipped with awing nut 76. It is apparent that the wing nut 76 may be loosened topermit change in the position of the gate for change in the level of thequenching liquid. The overflow outlet empties into a drainage trough 7Swhich in turn may empty into a waste pipe or may empty into a reservoirfor reuse. lf quenching liquid is continually supplied from the overheadpipe 24, the quenching liquid will overflow at a corresponding rate. lfno quenching liquid whatsoever is added, the tank will still overowbecause of the displacement of the liquid by the accumulating shot atthe bottom of the tank.

The heat exchange coil 43 may be adjusted to cause the surrounding Waterto be 10 F. lower than the upper water and may be simply a coil of theconfiguration shown for the use of cooling water. The inlet end of thecoil may be connected to any suitable water supply. If desirable, thecooling water may be continuously recirculated through the coil 43.

As heretofore stated, the tank may be movable relative to the feed unit30 to vary the distance that the molten bodies travel down the inclinedsurface of the interrupting member 46. For this purpose, the tank Zfdmay be mounted on a carriage 80 in the manner shown in Fig. 3, thecarriage having support wheels S2. `One end of the carriage 80 isequipped with a fixed nut 84- in screw-threaded engagement with a screw85 having a knurled head 86. The screw 85 is journaled in a fixedbracket 88 so that manual rotation of the screw by the knurled head 86moves the carriage 8G relative to the fixed bracket 88 for horizontaladjustment of the interrupting member 40 relative to the feed unit 30.

As heretofore stated, the feed unit 30 is mounted on an upright frame 2Sthat is separate from the tank 20 to permit the tank to be movedrelative to the feed unit. The previously mentioned vibrator 32 forvibrating the frame 28 and the feed unit 30 thereon may be a motorhaving a motor shaft 90 equipped with an eccentric weight 92.

In the preferred practice of the invention, the feed unit 30 is of theconstruction shown in Figs. 1, 4, 5 and 8. The feed unit comprises anelongated rectangular receptacle with two parallel side walls 94 and twoend walls 5. In the construction shown, a suitable thermometer 96extends through a bushing 98 in one of the side walls 94 to indicate theapproximate temperature of the liquid metal. A pyrometer (not shown) maybe additionally provided for accurate temperature readings.

Metal is continuously supplied to the feed unit 3i? from the melting pot34. The previously mentioned burner 55 keeps the metal in the feed unitheated to the desired temperature, for example a temperature of 130above the melting point of the metal. The burner 55 is provided with alongitudinal bathe 190 (Fig. 4) of angular configuration to facilitateheating the metal and maintaining the metal at the desired temperature.

The valve 38 is adjusted to supply melted metal to the feed unit atslightly above the rate at which the metal is dispensed by the feed unitin drop form. The excess metal flows into an elbow fitting 102 (Fig. 8)-at the end of the feed unit and the elbow fitting overfiows into asmall pot 104 that is mounted on a shelf 1515 on the side of the feedunit frame 28. It is a simple matter to vary the angle of the elbowfitting 102 thereby to vary the head or depth of the liquid metal in thefeed unit. In general, the depth of the molten metal is lowered for thelarger sizes of shot since larger feed openings are used for the largershot. The head of melted metal may range from one-half inch to one andone-fourth inches.

An important feature of the invention is the manner in which the feedunit 30 is constructed to form the liquid metal drops. For this purpose,the bottom of the feed unit is provided with a row of feed passages ofthe configuration shown in Fig. 5. Each feed passage is characterized bya conguration in which a restriction is followed by an expansion spaceand the expansion space is again followed by a restriction at the outletend of the passage where the metal drops are to be formed. A row of suchfeed passages in the bottom of the feed unit may be provided in variousways in various practices of the invention.

1n the construction shown in Figs. 4 and 5, the `bottom wall 168 of thefeed unit receptacle is formed with a relatively large bore 110 for eachof the feed passages. A pair of relatively thin metal sheets 112 and 114are clamped against the bottom wall 168 of the feed unit receptacle bymeans of a clamping plate 115. In the construction shown, the clampingplate is secured by screws 116 on opposite longitudinal sides of thefeed unit receptacle, the screws extending through opposite side flanges118 of the feed unit receptacle and extending through the two sheets 112and 114 into threaded engagement with the clamping plate 115. The uppermetal sheet 112 is provided with a row of relatively small apertures 120which register with the corresponding bores in the bottom wall 1118. Therelatively small apertures are countersunk to give them the downwardlytapered oonfiguration shown in Fig. 5. Thus the bottom edge of each ofthe apertures 120 serves as a restriction for the feed passage.

The second lower thin sheet 114 is provided with a row of largerapertures 122 that register with the small apertures 12@ of the sheet112. 'Ihe larger apertures 122 are also countersunk to give them adownwardly tapered configuration. The larger apertures 122 may beconsidered the outlet ends of the feed passages since the successivemetal drops form at the lower edges of these larger apertures. Theclamping plate 115 is formed with relatively large bores 124 thatregister with the apertures 122 of the thin sheet 114. The bores 124 arelarge enough to avoid contact with the successively formed drops ofmelted metal.

The rate of liow of the melted metal through each of the feed passagesis controlled by a corresponding regulating or retarding member 125which is formed at its lower end with a slender shank 126 terminating inan enlargement or head 128 that is suspended in the corresponding bore110 in the bottom wall 108. The head 128 overhangs the upper smalleraperture 120 in an adjustable manner for ample flow clearance around thecircumference of the head. As best shown in Fig. 4,

the receptacle of the feed unit has a cover in the formV of a heavyplate or bar 130 that is secured by suitable lateral screws 132. Thecover 130 has a vertical bore 134 for each of the regulating members12S, which bore is oversized for freedom of movement of the regulatingmember. Each regulating member is mounted by screw threads in anindividual metal plate 135, each o-f the individual metal plates beingsecured to the cover 130 by a pair of screws 136.

In the preferred practice of the invention, the threaded bore 138 ineac-h of the small metal plates 135 is oversized relative to thecorresponding regulating member 125 so that the regulating member hasappreciablefreedom to swing in any direction at its lower end. By virtueof this arrangement, the head 128 at the lower end of the regulatingmember is free for universal movement radially of the axis of thecorresponding feed passage and seeks a central equilibrium position atwhich the fluid flow is uniformly restricted around its circumference.In practice, the head 128 may accumulate dross but the head is free toshift in compensation for any such change in configuration.

In the initial embodiment of the invention, the bores 110 on .the bottomplate 108 of the feed unit receptacle are 0.270 inch 'diameter and theoutside diameter' of the head l12b-is approximately 0.250 inch. The twosheets 112 and 114 are 0.040 inch'thick. The diameter of the apertures120 vin sheet 112 is .020 *inch and the diameter of the lower, largerapertures 122 in sheet 114 is .025 inch which produces a largepercentage of shot .090 to 0.95 inch in diameter. Other shot sizes maybe obtained by employing other size apertures. Shot sizes may be variedin a limited degree by adjusting members 125 or by increasing `ordecreasing head pressure by manipulating elbow 102.

The regulating members 125 are adjusted relatively close to theapertures 120 in the upper sheet 112, the heads 12S being adjusted inthe range of .005-.010 inch from the sheet 112. The rate at which themelted metal seeps past the heads 128 through the smaller apertures 120into the` larger apertures 122 vis regulated to cause successive dropsof the desired size to be formed. The restriction of the flow throughthe smaller apertures 120 reduces the static head to facilitate theformation yof the drops. Adjusting the regulating members 125 to reducethe rate of flow through the smaller apertures has the effect ofincreasing the size of the drops. To make the apparatus capable ofproducing a wide range of sizes of shot, different sets of the pairs ofsheets 112 and 114 may be employed with cliiferent sizes 4of apertures120 and 122 for the different sizes of shot. As heretofore pointed out,the vibration of the feed unit by the vibrator 32 facilitates release ofthe drops and also makes the dimensions and adjustments less criticalfor the successful operation of the feed unit.

Fig. 6 shows how the interrupting member 40 of Fig. 4 may be replaced bya member 40a which is mounted on a pair of angular side brackets 140 bysuitable screws 142. The upper end of the tilted member extendsrelatively close to the wall of the tank but is provided with aplurality of bores 144 for the free passage of bubbles to the surface ofthe quenching liquid 22. The upper end of the member 40a is cut away toform a shoulder 14S which serves as a barrier to prevent the turbulencethat is created by the bubbles from extending over the upper surface ofthe member 40a. For the purpose of varying the elevation of the surfaceof the member 40a, a set of such members of different thicknesses isprovided for interchangeable use.

Fig. 7 shows an interrupting member 40h which also may be substitutedfor the member 40 in Fig. 4. The member 4011 is of the same generalconstruction as the member 40 but has a removable top panel 146. Theelevation of the top surface of the member 40h may be varied byselecting a panel 146 from a set of interchangeable panels of varyingthickness.

Fig. 9 shows how a set of tankszta, 2Gb, 20c, etc., may be employedinterchangeably with the feed unit 30. The interchangeable tanks rollfreely into position to receive t-he melted metal drops from the feedunit and serve as containers for transporting the formed shot to otherequipment for processing and classifying the sho-t. Each of theinterchangeable tanks may be provided with an electrical heater 148which may be plugged into a suitable current source by a cable 150. Eachof the interchangeable tanks is provided with the usual heat exchangecoil 43, the opposite ends of which have quick disconnect ttings forconnection to a pair of corresponding flexible hoses 152 and 154'forcirculating water.

Figs. l() and ll show an arrangement which may be used in some practicesof the invention for interrupting the fall of the molten metal bodiesand to impart spin to the metal bodies before releasing the metal bodiesfor continuing their fall through the quenching liquid. In thisarrangement, a circular feed unit 3001s employed of the same generalconstruction as the previously described feed unit 30. The feed unit 30ahas a series of feed"passa`g'e`s 'arrangedin a circle'"to releasesuccessive` drops` 'of melted metal'to fall'lona submergeddsc-shaped 8interrupting member 40e which may be made of suitable wood; The disc40C' isV mounted on an .uprightshaftV 15S for rotation about an uprightaxis at; a rat'eto cause the molten metal bodies thereon to travel' to,theV outer( edge of thel disc; Thus the molten metal bodies aremomentarily interrupted in their fall and are caused to spin in moltenstate as they resume their fall.

My description in specic detail of the selected practices of theinvention will suggest various changes, substitutions and otherdepartures from my disclosure within the spirit and scope of theappended claims.

I claim: l

l. A method of forming spherical metal pellets, including the steps of:releasing bodies of the metal in the form `of liquid drops to fall intoa body of quenching liquid onto a surface of a transverse member in thequenching liquid of absorbent material of low thermal conductivity whilethe bodies are still molten; causing the molten bodies to move alongsaid surface for imparting spin to the molten bodies and releasing thespinning bodies from said surface to continue to fall through thequenching liquid to cause the spinning metal bodies Ito solidify Whilefalling.

2. A method as set forth in claim l in which said material is fibrousliquid-absorbent material.

3, A method as set forth in claim 2 in which said material is Wood. v

4. A method of forming spherical metal pellets, including the steps of:releasing bodies of the metal in the form of liquid drops to fall into abody of quenching liquid onto a surface of a member of low thermalconductivity extending transversely across the paths of fall While themetal bodies are sti-ll molten; rotating said member about an uprightaxis to cause the molten bodies to be urged across said surface bycentrifugal force for imparting spin Ito the molten bodies; andcontinuing the fall of the spinning metal bodies in the quenching liquidto permit the metal bodies to solidify while falling.

5. A method of forming spherical metal pellets with minimum surfaceoxidation, including the steps of: releasing bodies of the metal in theform of liquid drops immediately above the surface ofa body of quenchingliquid with minimum exposure of the drops to air above the liquidsurface; breaking the fall of the metal bodies in the liquid while theyare still molten by impact against a surface of porous material of lowthermal conductivity; causing the molten bodies xto travel across saidsurface lto impart spin to the molten bodies; and continuing the fall ofthe spinning metal bodies in the quenching liquid to permit the metalbodies to solidify while falling.

6. A method of forming spherical metal pellets, including the steps of:releasing bodies of the metal in the form of liquid drops to fall into abody of quenching liquid onto a surface of a member of fibrous materialof low thermal conductivity while the metal bodies are molten to causethe formation of vapor between the molten metal bodies and said surfaceto cause rebound of the molten metal bodies for interrupting the fall ofthe molten bodies; causing the molten bodies to travel along said lsurface with the consequent imparting of spinto the metal bodies; andreleasing the metal bodies to continue to fall through the quenchingliquid and to solidify while falling.

7. An apparatus to form spherical metal pellets, comprising: a reservoirto hold a supply of the metal in melted form; a plurality of passagemeans to release bodies of the melted metal from the reservoir in dropform; means confining a body of quenching liquid close to said passagemeans in the path of -fall of the metal bodies from said passage meansto cause the metal bodies to fall through the quenching liquid and tosolidify while falling; and means in said liquid extending acrosssaidinterriiptigmmeans providing an inclined surface Q blocking the pathor fall of the metal bodies from said passage means, said surface beingmade of liquid-absorbing material of low thermal conductivity and beinginclined from horizontal to cause the metal bodies to travel along theinclined surface While they are still molten thereby to impart spin tothe molten bodies.

8. A combination as set forth in claim 7 which includes means to adjustthe vertical distance between said inclined surface and said passagemeans.

9. An apparatus as set forth in claim 7 which includes means to adjustthe inclination of said surface.

l0. An apparatus as set forth in claim 7 which includes means to varythe distance the molten metal bodies travel along said surface.

1l. An apparatus to form spherical metal pellets, comprising: areservoir to hold a supply of the metal in melted form; a plurality ofpassage means to release bodies of the melted metal from the reservoirin drop form; means confining a body of quenching liquid in the path offall of the metal bodies from said passage means to cause the metalbodies to fall through the quenching liquid and to solidify Whilefalling; means in said liquid extending across the paths of fall of themetal bodies to interrupt the falls of the metal bodies while the metalbodies are still molten, said interrupting means having a surface of lowthermal conductivity positioned transversely of the paths of fall of themetal bodies from said passage means; and means to rotate saidinterrupting means about an upright axis to cause the metal bodies tomove along said surface by centrifugal force to impart spin tothe metalbodies while they are still molten.

References Cited in the le of this patent UNITED STATES PATENTS

